1. Field of the Invention
The present invention relates to wayside signaling generally and more particularly to wayside signal acknowledgment systems.
2. Description of Related Art
A wide variety of wayside signal systems are known to the prior art. Traditional wayside signaling systems comprise one or more colored signal lights that are mounted on poles alongside a train track at various locations such as near the beginning of a block of track or near grade crossings, sidings, switches, etc. The signal lights indicate such things as speed restrictions and the status of the next block of track. On some railroads there are over 125 different colored light signal indications that must be recognized and obeyed. An engineer/operator is required to observe the lights and operate the train accordingly. However, because engineers/operators are human, mistakes which can cause serious accidents are sometimes made. Such mistakes include the failure to observe signal lights and misinterpretation as to the meaning of the signal lights.
Several known systems address this problem in one form or another. For example, a system described in U.S. Pat. No. 6,112,142 (the contents of which are hereby incorporated by reference herein), which is owned by the assignee of the present invention, provides a signal comparator system and method in which and engineer and a trainman are each provided with a combined display/input device referred to therein as a pendant. In that system, both the engineer and the trainman must agree, by pressing corresponding buttons on the pendant, as to the meaning of the signal as indicated by the lights. If both the engineer and the trainman agree as to the meaning of the signal, that system will automatically enforce any restrictions corresponding to the signal. If the engineer and the trainman do not agree as to the meaning of the signal, or do not obey any restrictions corresponding to the signal (e.g., the signal indicates stop, but the brakes are not activated), the system will take corrective action to enforce the signal and/or stop the train. However, this system, while providing several advantages over other known systems, has some drawbacks. First, it requires the presence of both an engineer and a trainman. Second, it is susceptible to error or intentional defeat by an engineer and a trainman who enter (accidentally or purposely) the wrong signal information.
In another known system, referred to as Cab Signal, a display is provided in the cab for the engineer/operator and wayside signals are transmitted to the system and shown on the display. The Cab Signal system forces the engineer/operator to acknowledge signals that are more restrictive than the current signal and, in some systems, forces the engineer/operator to obey the more restrictive signal. However, this system does not force an engineer/operator to acknowledge less restrictive signals. This is disadvantageous because if an engineer/operator misses a less restrictive signal, the engineer/operator may miss an opportunity to operate the train more efficiently by increasing the speed of the train.
What is needed is a system and method that overcomes these and other deficiencies in known systems.